One thing I have noticed is that there are nastier virus's around compared to years ago.
I have a theory about the nasty virus's. A lot of folks don't fully knock out a virus when they get one, either by not doing everything they can to get well, or if it is a bacterial infection, like I had, they don't finish the full course of their antibiotic. What this does is kill all the weakest germs and leave the strong ones to survive.
Another piece of this is similar to what happens when people have untreated allergies. If you suffer ongoing allergies, it runs you down and you become more susceptible to getting sick. Many of us lead ridiculously hectic lives. We don't get enough rest. We worry a lot. These things not only deplete you mentally, but physically and like with an allergy, you end up being more likely to get sick.
All this constant hand washing and doing everything to avoid germs may in fact be counter affective. We need some germs, it is how we build immunity to others. If our environment it too sterile, we never build that immunity.